Crucial amendments to the Constitution for UPSC exam preparation include the 73rd and 74th amendments, which enhance local self-governance through the establishment of Panchayati Raj institutions and urban municipalities. The 86th amendment, introducing the Right to Education, is significant as it ensures free and compulsory education for children. The 42nd amendment, known as the "Mini-Constitution," is essential for understanding the judicial review and fundamental rights’ amendments. Familiarity with these amendments helps candidates appreciate their implications for governance and policy-making, forming an integral part of the syllabus relevant for both the prelims and mains exams.